You receive an annual report of the results of your city's tap water testing. The report shows that there are small amounts (a fraction of a milligram per liter) of a water-soluble chemical called dichloroethene present. You want to determine whether this is a toxic chemical. Describe a study that could be conducted to measure its toxicity. Draw a sample dose-response graph for mortality that includes a threshold dose and LD50. Make sure you label each axis.